EP3693627B1 - Multimode powertrains for rotorcraft - Google Patents
Multimode powertrains for rotorcraft Download PDFInfo
- Publication number
- EP3693627B1 EP3693627B1 EP20152333.9A EP20152333A EP3693627B1 EP 3693627 B1 EP3693627 B1 EP 3693627B1 EP 20152333 A EP20152333 A EP 20152333A EP 3693627 B1 EP3693627 B1 EP 3693627B1
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- EP
- European Patent Office
- Prior art keywords
- main
- drive system
- engine
- assembly
- coupled
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- 230000002457 bidirectional effect Effects 0.000 claims description 19
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Images
Classifications
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16D—COUPLINGS FOR TRANSMITTING ROTATION; CLUTCHES; BRAKES
- F16D11/00—Clutches in which the members have interengaging parts
- F16D11/14—Clutches in which the members have interengaging parts with clutching members movable only axially
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16D—COUPLINGS FOR TRANSMITTING ROTATION; CLUTCHES; BRAKES
- F16D41/00—Freewheels or freewheel clutches
- F16D41/06—Freewheels or freewheel clutches with intermediate wedging coupling members between an inner and an outer surface
- F16D41/069—Freewheels or freewheel clutches with intermediate wedging coupling members between an inner and an outer surface the intermediate members wedging by pivoting or rocking, e.g. sprags
- F16D41/07—Freewheels or freewheel clutches with intermediate wedging coupling members between an inner and an outer surface the intermediate members wedging by pivoting or rocking, e.g. sprags between two cylindrical surfaces
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B64—AIRCRAFT; AVIATION; COSMONAUTICS
- B64C—AEROPLANES; HELICOPTERS
- B64C27/00—Rotorcraft; Rotors peculiar thereto
- B64C27/04—Helicopters
- B64C27/12—Rotor drives
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B64—AIRCRAFT; AVIATION; COSMONAUTICS
- B64D—EQUIPMENT FOR FITTING IN OR TO AIRCRAFT; FLIGHT SUITS; PARACHUTES; ARRANGEMENTS OR MOUNTING OF POWER PLANTS OR PROPULSION TRANSMISSIONS IN AIRCRAFT
- B64D35/00—Transmitting power from power plant to propellers or rotors; Arrangements of transmissions
- B64D35/08—Transmitting power from power plant to propellers or rotors; Arrangements of transmissions characterised by the transmission being driven by a plurality of power plants
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16D—COUPLINGS FOR TRANSMITTING ROTATION; CLUTCHES; BRAKES
- F16D1/00—Couplings for rigidly connecting two coaxial shafts or other movable machine elements
- F16D1/10—Quick-acting couplings in which the parts are connected by simply bringing them together axially
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16D—COUPLINGS FOR TRANSMITTING ROTATION; CLUTCHES; BRAKES
- F16D25/00—Fluid-actuated clutches
- F16D25/08—Fluid-actuated clutches with fluid-actuated member not rotating with a clutching member
- F16D25/082—Fluid-actuated clutches with fluid-actuated member not rotating with a clutching member the line of action of the fluid-actuated members co-inciding with the axis of rotation
- F16D25/083—Actuators therefor
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16D—COUPLINGS FOR TRANSMITTING ROTATION; CLUTCHES; BRAKES
- F16D41/00—Freewheels or freewheel clutches
- F16D41/04—Freewheels or freewheel clutches combined with a clutch for locking the driving and driven members
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B64—AIRCRAFT; AVIATION; COSMONAUTICS
- B64C—AEROPLANES; HELICOPTERS
- B64C27/00—Rotorcraft; Rotors peculiar thereto
- B64C27/04—Helicopters
- B64C27/06—Helicopters with single rotor
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16D—COUPLINGS FOR TRANSMITTING ROTATION; CLUTCHES; BRAKES
- F16D1/00—Couplings for rigidly connecting two coaxial shafts or other movable machine elements
- F16D1/10—Quick-acting couplings in which the parts are connected by simply bringing them together axially
- F16D2001/103—Quick-acting couplings in which the parts are connected by simply bringing them together axially the torque is transmitted via splined connections
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16D—COUPLINGS FOR TRANSMITTING ROTATION; CLUTCHES; BRAKES
- F16D11/00—Clutches in which the members have interengaging parts
- F16D2011/004—Clutches in which the members have interengaging parts using an internal or intermediate axially slidable sleeve, coupling both components together, whereby the intermediate sleeve is arranged internally at least with respect to one of the components
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16D—COUPLINGS FOR TRANSMITTING ROTATION; CLUTCHES; BRAKES
- F16D2121/00—Type of actuator operation force
- F16D2121/02—Fluid pressure
- F16D2121/04—Fluid pressure acting on a piston-type actuator, e.g. for liquid pressure
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16D—COUPLINGS FOR TRANSMITTING ROTATION; CLUTCHES; BRAKES
- F16D41/00—Freewheels or freewheel clutches
- F16D41/06—Freewheels or freewheel clutches with intermediate wedging coupling members between an inner and an outer surface
- F16D41/069—Freewheels or freewheel clutches with intermediate wedging coupling members between an inner and an outer surface the intermediate members wedging by pivoting or rocking, e.g. sprags
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16D—COUPLINGS FOR TRANSMITTING ROTATION; CLUTCHES; BRAKES
- F16D47/00—Systems of clutches, or clutches and couplings, comprising devices of types grouped under at least two of the preceding guide headings
- F16D47/04—Systems of clutches, or clutches and couplings, comprising devices of types grouped under at least two of the preceding guide headings of which at least one is a freewheel
Definitions
- the present disclosure relates, in general, to powertrains operable for use on rotorcraft and, in particular, to multimode powertrains operable to selectively utilize secondary engine power independent of or together with main engine power to drive the main rotor, the tail rotor and/or the accessories of a rotorcraft.
- Certain rotorcraft are capable of taking off, hovering and landing vertically.
- One such rotorcraft is a helicopter, which has one or more main rotors that provide lift and thrust to the aircraft.
- the main rotors not only enable hovering and vertical takeoff and landing, but also enable forward, backward and lateral flight. These attributes make helicopters highly versatile for use in congested, isolated or remote areas.
- Another such rotorcraft is a tiltrotor aircraft, which has a set of proprotors that can change their plane of rotation based on the operation being performed.
- Tiltrotor aircraft typically have a pair of nacelles mounted near the outboard ends of a fixed wing with each nacelle housing a propulsion system that provides torque and rotational energy to a proprotor.
- the nacelles are rotatable relative to the fixed wing such that the proprotors have a generally horizontal plane of rotation providing vertical thrust for takeoff, hovering and landing, much like a conventional helicopter, and a generally vertical plane of rotation providing forward thrust for cruising in forward flight with the fixed wing providing lift, much like a conventional propeller driven airplane.
- the power demand of a rotorcraft can change significantly based upon the operating mode of the rotorcraft. For example, significantly more power may be demanded during takeoff, hover or dash operations compared to cruise or preflight operations.
- Certain rotorcraft utilize auxiliary power units to supply preflight power during startup procedures and to start the main engine of the rotorcraft. It has been found, however, that these auxiliary power units are not operable to provide supplemental power or emergency power to the main rotor during flight operation.
- US 3 362 255 describes a mechanism for transmitting power from a common power source to two, receiving members or groups of receiving members, comprising three coaxial shafts respectively connected permanently to said common power source and to said two members or groups of members, and coupled or decoupled in pairs by means of three automatically actuated clutching means interposed between each pair of shafts, a lock-out means avoiding any action of said first clutching means and means for preventing any accidental locking-in of the first clutching means
- US 2018/172088 describes a low-backlash multimode clutch including a one-way bearing allowing rotation in a first direction as well as a number of actuatable pawls in one race and a number of receiving slots having engagement faces in the other race.
- the engagement faces are tilted such that when the pawls are actuated, any torque applied in the first direction tends to force the pawls outward but the pawls are retained inward, such as by actuator rods.
- the one-way clutch may be selectively locked and unlocked with zero backlash against the one-way bearing.
- US 2019/032760 describes a switchable one-way clutch that is able to switch between operating as a one-way clutch and a clutch that locks in both directions.
- the clutch includes an inner race, and an outer race that includes an inner surface with a plurality of ramped profiles.
- a control plate is located radially outward from the inner race and moveable in an axial direction relative to the outer race.
- a plurality of rollers are contactable with the outer and inner races.
- a roller cage is configured to position and contain the plurality of rollers.
- a hydraulic piston is coupled to an actuator arm, such that movement of the piston along the axis moves the actuator arm along the axis. To switch and engage the clutch such that rotation is locked in both directions, the piston and actuator arm move axially to hold the control plate and attached roller cage against rotation.
- the present disclosure is directed to a selectable clutch assembly according to appended claim 1.
- the freewheeling unit may be a sprag clutch.
- the bypass assembly may include an actuator configured to shift the bypass assembly between the engaged position and the disengaged position. In certain embodiments, the bypass assembly may include a locking assembly configured to maintain the bypass assembly in the engaged position and in the disengaged position.
- the present disclosure is directed to a multimode powertrain for a rotorcraft.
- the multimode powertrain includes a main drive system, a secondary drive system and a selectable clutch assembly according to appended claim 1 positioned between the main and the secondary drive systems.
- the main drive system may include a main engine, a main rotor gearbox coupled to the main engine and a tail rotor gearbox coupled to the main rotor gearbox and the secondary drive system may include a secondary engine.
- the selectable clutch assembly In a preflight configuration, the selectable clutch assembly is in the disengaged position, the main engine is not operating and the secondary engine provides power to at least one rotorcraft accessory coupled to the secondary drive system.
- the selectable clutch assembly is in the engaged position, the main engine provides power to the main rotor gearbox and the tail rotor gearbox and the secondary engine provides power to at least one rotorcraft accessory coupled to the secondary drive system and to the main drive system through the selectable clutch assembly.
- the selectable clutch assembly In a high efficiency configuration, the selectable clutch assembly is in the engaged position, the secondary engine is not operating, the main engine provides power to the main rotor gearbox, the tail rotor gearbox and the secondary drive system through the selectable clutch assembly to power at least one rotorcraft accessory coupled to the secondary drive system.
- the selectable clutch assembly In an enhanced auto rotation configuration, the selectable clutch assembly is in the engaged position, the main engine is not operating and the secondary engine provides power to the main drive system through the selectable clutch assembly including to the main rotor gearbox.
- the secondary engine may be configured to generate between about 5 percent and about 20 percent of the horsepower of the main engine. In other embodiments, the secondary engine may be configured to generate between about 10 percent and about 15 percent of the horsepower of the main engine.
- the present disclosure is directed to a rotorcraft that includes a main drive system having a main engine, a main rotor gearbox coupled to the main engine and a tail rotor gearbox coupled to the main rotor gearbox.
- a main rotor is coupled to the main rotor gearbox and is rotatable thereby.
- a tail rotor is coupled to the tail rotor gearbox and is rotatable thereby.
- a secondary drive system includes a secondary engine.
- a selectable clutch assembly according to appended claim 1 is positioned between the main and the secondary drive systems.
- the devices, members, apparatuses, and the like described herein may be positioned in any desired orientation.
- the use of terms such as “above,” “below,” “upper,” “lower” or other like terms to describe a spatial relationship between various components or to describe the spatial orientation of aspects of such components should be understood to describe a relative relationship between the components or a spatial orientation of aspects of such components, respectively, as the devices described herein may be oriented in any desired direction.
- the term “coupled” may include direct or indirect coupling by any means, including by mere contact or by moving and/or non-moving mechanical connections.
- a rotorcraft in the form of a helicopter is schematically illustrated and generally designated 10.
- the primary propulsion assembly of helicopter 10 is a main rotor assembly 12.
- Main rotor assembly 12 includes a plurality of rotor blades 14 extending radially outward from a main rotor hub 16.
- Main rotor assembly 12 is coupled to a fuselage 18 and is rotatable relative thereto.
- the pitch of rotor blades 14 can be collectively and/or cyclically manipulated to selectively control direction, thrust and lift of helicopter 10.
- a tailboom 20 is coupled to fuselage 18 and extends from fuselage 18 in the aft direction.
- An anti-torque system 22 includes a tail rotor assembly 24 coupled to an aft end of tailboom 20. Anti-torque system 22 controls the yaw of helicopter 10 by counteracting the torque exerted on fuselage 18 by main rotor assembly 12.
- helicopter 10 includes a vertical tail fin 26 that provide stabilization to helicopter 10 during high speed forward flight.
- helicopter 10 includes wing members 28 that extend laterally from fuselage 18 and wing members 30 that extend laterally from tailboom 20.
- Wing members 28, 30 provide lift to helicopter 10 responsive to the forward airspeed of helicopter 10, thereby reducing the lift requirement on main rotor assembly 12 and increasing the top speed of helicopter 10
- Main rotor assembly 12 and tail rotor assembly 24 receive torque and rotational energy from a main engine 32.
- Main engine 32 is coupled to a main rotor gearbox 34 by suitable clutching and shafting.
- Main rotor gearbox 34 is coupled to main rotor assembly 12 by a mast 36 and is coupled to tail rotor assembly 24 by tail rotor drive shaft 38.
- a secondary engine 40 is coupled to tail rotor drive shaft 38 by a secondary engine gearbox 42 that provides suitable clutching therebetween.
- main engine 40, main rotor gearbox 34, tail rotor drive shaft 38, secondary engine 40 and secondary engine gearbox 42 as well as the various other shafts and gearboxes coupled therein may be considered as the multimode powertrain of helicopter 10.
- Secondary engine 40 is operable as an auxiliary power unit to provide preflight power to the accessories of helicopter 10 such as electric generators, hydraulic pumps and the like as well as to provide the power required to start main engine 32.
- secondary engine 40 is operable to provide supplemental power that is additive with the power provided by main engine 32 during, for example, high power demand conditions including takeoff, hover and dash operations.
- Secondary engine 40 is also operable to provide emergency power to main rotor assembly 12.
- secondary engine 40 is operable to provide emergency power to enhance the autorotation and flare recovery maneuver of helicopter 10.
- Use of secondary engine 40 not only enhances the safety of helicopter 10 but also increases the efficiency of helicopter 10. For example, having the extra power provided by secondary engine 40 during high power demand operations allows main engine 32 to be downsized for more efficient single engine operations such as during cruise operations.
- helicopter 10 is merely illustrative of a variety of aircraft that can implement the embodiments disclosed herein.
- the multimode powertrain of the present disclosure may be implemented on any rotorcraft.
- Other aircraft implementations can include hybrid aircraft, tiltwing aircraft, tiltrotor aircraft, quad tiltrotor aircraft, unmanned aircraft, gyrocopters, propeller-driven airplanes, compound helicopters, drones and the like.
- the multimode powertrain of the present disclosure can be integrated into a variety of aircraft configurations. It should be appreciated that even though aircraft are particularly well-suited to implement the embodiments of the present disclosure, non-aircraft vehicles and devices can also implement the embodiments.
- Multimode powertrain 100 includes a main engine 102 such as a turbo shaft engine capable of producing 2000 to 4000 horsepower or more, depending upon the particular implementation.
- Main engine 102 is coupled to a freewheeling unit depicted as sprag clutch 104 that acts as a one-way clutch enabling a driving mode wherein torque from main engine 102 is coupled to main rotor gearbox 106 when the input side rotating speed to sprag clutch 104 is matched with the output side rotating speed from sprag clutch 104.
- sprag clutch 104 has an over running mode wherein main engine 102 is decoupled from main rotor gearbox 106 when the input side rotating speed of sprag clutch 104 is less than the output side rotating speed of sprag clutch 104.
- Operating sprag clutch 104 in the over running mode allows, for example, main rotor 108 of helicopter 10 to engage in autorotation in the event of a failure of main engine 102.
- main rotor gearbox 106 is coupled to sprag clutch 104 via a suitable drive shaft.
- main rotor gearbox 106 is coupled to main rotor 108 by a suitable mast.
- Main rotor gearbox 106 includes a gearbox housing and a plurality of gears, such as planetary gears, used to adjust the engine output to a suitable rotational speed so that main engine 102 and main rotor 108 may each rotate at optimum speed during flight operations of helicopter 10.
- Main rotor gearbox 106 is coupled to a tail rotor gearbox 110 via a suitable tail rotor drive shaft.
- Tail rotor gearbox 110 includes a gearbox housing and a plurality of gears that may adjust the main rotor gearbox output to a suitable rotational speed for operation of tail rotor 112.
- Main engine 102, sprag clutch 104, main rotor gearbox 106 and tail rotor gearbox 110 as well as the various shafts and gearing systems coupled therewith may be considered the main drive system of multimode powertrain 100.
- Multimode powertrain 100 includes a secondary engine 114 such as a turbo shaft engine capable of producing 200 to 400 horsepower or more, depending upon the particular implementation.
- secondary engine 114 may generate between about 5 percent and about 20 percent of the horsepower of main engine 102. In other embodiments, secondary engine 114 may generate between about 10 percent and about 15 percent of the horsepower of main engine 102.
- Secondary engine 114 is coupled to a freewheeling unit depicted as sprag clutch 116 that acts as a one-way clutch enabling a driving mode wherein torque from secondary engine 114 is coupled through sprag clutch 116 from the input side to the output side.
- sprag clutch 116 has an over running mode wherein secondary engine 114 is decoupled from torque transfer with sprag clutch 116 when the input side rotating speed of sprag clutch 116 is less than the output side rotating speed of sprag clutch 116.
- Operating sprag clutch 116 in the over running mode allows, for example, main engine 102 to drive the rotorcraft accessories such as one or more generators 118, one or more hydraulic pumps 120 or other accessories 122 when secondary engine 114 is not operating, as discussed herein.
- Secondary engine 114 and sprag clutch 116 as well as the various shafts and gearing systems coupled therewith may be considered the secondary drive system of multimode powertrain 100.
- a selectable clutch assembly 124 Disposed between the main drive system and the secondary drive system of multimode powertrain 100 is a selectable clutch assembly 124 that has a unidirectional torque transfer mode and a bidirectional torque transfer mode.
- torque can be driven from the main drive system to the secondary drive system of multimode powertrain 100 but torque cannot be driven from the secondary drive system to the main drive system of multimode powertrain 100.
- torque can be driven from the main drive system to the secondary drive system of multimode powertrain 100 and torque can be driven from the secondary drive system to the main drive system of multimode powertrain 100.
- selectable clutch assembly 124 includes a freewheeling unit depicted as sprag clutch 126 and a bypass assembly 128.
- Sprag clutch 126 acts as a one-way clutch enabling a driving mode wherein torque from the main drive system is coupled through sprag clutch 126 from the input side to the output side.
- Sprag clutch 126 also has an over running mode wherein the main drive system is decoupled from torque transfer with sprag clutch 126 when the input side rotating speed of sprag clutch 126 is less than the output side rotating speed of sprag clutch 126.
- selectable clutch assembly 124 is in its unidirectional torque transfer mode.
- selectable clutch assembly 124 can be disabled by engaging bypass assembly 128 with sprag clutch 126.
- bypass assembly 128 prevents sprag clutch 126 from operating in the over running mode
- selectable clutch assembly 124 is in its bidirectional torque transfer mode.
- multimode powertrain 100 is in a preflight configuration in which main engine 102 is not yet operating as indicated by the dashed lines between the components of the main drive system. As the main drive system is not turning, no torque is being applied to selectable clutch assembly 124 as indicated by the dashed lines therebetween. In addition, selectable clutch assembly 124 is in the unidirectional torque transfer mode wherein bypass assembly 128 is disengaged from sprag clutch 126. In the preflight configuration, secondary engine 114 is operating and providing torque and rotational energy within the secondary drive system, as indicated by the solid lines and arrowheads.
- secondary engine 114 is driving the input side of sprag clutch 116, which causes the output side of sprag clutch 116 to drive an output shaft and/or output gear system.
- the output torque from sprag clutch 116 is used to drive the rotorcraft accessories such as one or more generators 118, one or more hydraulic pumps 120 as well as other accessories 122.
- the pilot of helicopter 10 can proceed through the startup procedure and can use power from secondary engine 114 to start main engine 102.
- torque is delivered through the main drive system as indicated by the solid lines and arrowheads between the components within the main drive system, as best seen in figure 2B .
- torque may be applied to selectable clutch assembly 124.
- selectable clutch assembly 124 in order to shift selectable clutch assembly 124 from the unidirectional torque transfer mode to the bidirectional torque transfer mode, power should be applied to the input side of sprag clutch 126 from the main drive system such that the input side and the output side of sprag clutch 126 are turning together.
- Bypass assembly 128 can now be actuated from the disengaged position to the engaged position placing selectable clutch assembly 124 in the bidirectional torque transfer mode.
- the operations of engaging and disengaging bypass assembly 128 may be pilot controlled and/or may be automated by the flight control computer of helicopter 10 and may determined according to the operating conditions of helicopter 10.
- power from secondary engine 114 may not only drive the rotorcraft accessories but may also be used to augment the power of main engine 102 within the main drive system, as indicated by the solid lines and arrowhead from selectable clutch assembly 124 to the main drive system in figure 2B .
- This configuration may be referred to as the enhanced power configuration of multimode powertrain 100 wherein main engine 102 and secondary engine 114 are operating together and selectable clutch assembly 124 is in the bidirectional torque transfer mode.
- the enhanced power configuration of multimode powertrain 100 is particularly useful during high power demand operations such as during takeoff, hover or dash operations.
- selectable clutch assembly 124 is preferably maintained in its bidirectional torque transfer mode during all flight operations. Selectable clutch assembly 124, however, is a fail safe component in that even if selectable clutch assembly 124 is shifted to the disengaged position and thus the unidirectional torque transfer mode, main engine 102 still drives torque and rotation energy through selectable clutch assembly 124 to operate the rotorcraft accessories.
- selectable clutch assembly 124 be maintained in its bidirectional torque transfer mode as a safety feature in the event of a failure in main engine 102 during flight, as indicated by the dashed lines between main engine 102 and sprag clutch 104 in figure 2D .
- an autorotation maneuver may be performed in which the descent rate of helicopter 10 is reduced using the aerodynamic force of the air moving up through main rotor 108.
- helicopter 10 Upon final approach during the autorotation landing, helicopter 10 then performs a flare recovery maneuver in which the kinetic energy of main rotor 108 is converted into lift using aft cyclic control.
- Both the autorotation maneuver and the flare recovery maneuver are enhanced by operating secondary engine 114 and sending power through selectable clutch assembly 124 to the main drive system, as indicated by the solid lines and arrowhead therebetween, and more particularly by sending power to main rotor 108 as indicated by the solid lines and arrowheads leading thereto.
- rotational energy is also sent to sprag clutch 104, which is operating in its over running mode while main engine 102 is not operating.
- This configuration may be referred to as the enhanced autorotation configuration of multimode powertrain 100 wherein main engine 102 is down but secondary engine 114 is providing power to main rotor 108 through selectable clutch assembly 124, which is in the bidirectional torque transfer mode.
- Selectable clutch assembly 200 includes a freewheeling unit depicted as sprag clutch 202 and a bypass assembly 204.
- selectable clutch assembly 200 has a unidirectional torque transfer mode and a bidirectional torque transfer mode.
- torque can be driven from the input of side sprag clutch 202, including input gear 205, to the output side of sprag clutch 202, including output gear 206, but torque cannot be driven from output gear 206 to input gear 205.
- torque can be driven from input gear 205 to output gear 206 and torque can be driven from output gear 206 to input gear 205.
- selectable clutch assembly 200 operates with the functionality of sprag clutch 202 wherein torque and rotational energy from the main drive system of helicopter 10, which is coupled to input gear 205, is operable to drive the secondary drive system of helicopter 10, which is coupled to output gear 206. Torque and rotational energy from the secondary drive system of helicopter 10, however, is not operable to drive the main drive system of helicopter 10 as sprag clutch 202 will be operating in its over running mode.
- selectable clutch assembly 200 operates with the functionality of a connected shaft wherein torque and rotational energy from the main drive system of helicopter 10 is operable to drive the secondary drive system of helicopter 10 and torque and rotational energy from the secondary drive system of helicopter 10 is operable to drive the main drive system of helicopter 10.
- Selectable clutch assembly 200 is operated between the unidirectional and bidirectional torque transfer modes by actuating bypass assembly 204 between its disengaged and engaged positions.
- bypass assembly 204 includes an actuator depicted as hydraulic actuator 208.
- the actuator of bypass assembly 204 could be an electrical actuator, a mechanical actuator or other suitable actuation device.
- Hydraulic actuator 208 includes an actuation shaft 210 that is movable between first and second positions responsive to hydraulic pressure operating on a piston end 212 of actuation shaft 210, which is disposed within a hydraulic cylinder 214 of hydraulic actuator 208.
- Actuation shaft 210 is coupled to bypass coupling 216 at bearing assembly 218 that provides for relative rotation therebetween.
- bypass assembly 204 includes a mechanical locking assembly depicted as ball-detent locking mechanism 220.
- a biasing element depicted as wave spring 222 is positioned between actuation shaft 210 and bearing assembly 218.
- selectable clutch assembly 200 is in the unidirectional torque transfer mode wherein bypass assembly 204 is in the disengaged position.
- inner splines 224 of bypass coupling 216 are in mesh with outer splines (not visible) of inner shaft 226 of the output side of sprag clutch 202.
- bypass coupling 216 also rotates.
- Outer splines (not visible) of bypass coupling 216 are out of mesh with inner splines 228 of outer race 230 of the input side of sprag clutch 202.
- bypass coupling 216 may rotate independent of the input side of sprag clutch 202 when sprag clutch 202 is operating in its over running mode.
- actuation shaft 210 In this disengaged position, actuation shaft 210 is in its first position relative to hydraulic cylinder 214 and is secured in the first position by ball-detent locking mechanism 220 as one or more balls are engaged with a first detent groove 232 of actuation shaft 210.
- selectable clutch assembly 200 When it is desired to operate selectable clutch assembly 200 from the unidirectional to the bidirectional torque transfer mode, the input side of sprag clutch 202 is used to drive the output side of sprag clutch 202 such that bypass coupling 216 and outer race 230 will be rotating at the same speed. Hydraulic pressure may then be used to bias actuation shaft 210 toward sprag clutch 202.
- actuation shaft 210 When the force on piston end 212 is sufficient to overcome the locking force generated by ball-detent locking mechanism 220, actuation shaft 210 will shift toward sprag clutch 202 causing the outer splines of bypass coupling 216 to mesh with inner splines 228 of outer race 230, thereby shifting bypass assembly 204 to the engaged position and selectable clutch assembly 200 to the bidirectional torque transfer mode, as best seen in figure 3B .
- Wave spring 222 assists in overcoming any misalignment in the clocking of the outer splines of bypass coupling 216 and inner splines 228 of outer race 230 by allowing full actuation of actuation shaft 210 while maintaining pressure between bypass coupling 216 and outer race 230 so that when inner shaft 226 and outer race 230 start to rotate relative to each other, outer splines of bypass coupling 216 will mesh with inner splines 228 of outer race 230.
- bypass coupling 216 rotates therewith.
- selectable clutch assembly 200 operates with the functionality of a connected shaft.
- sprag clutch 202 When it is desired to operate selectable clutch assembly 200 from the bidirectional to the unidirectional torque transfer mode, the input side of sprag clutch 202 preferably drives the output side of sprag clutch 202. Hydraulic pressure may then be used to bias actuation shaft 210 away from sprag clutch 202. When the force on piston end 212 is sufficient to overcome the locking force generated by ball-detent locking mechanism 220, actuation shaft 210 will shift away from sprag clutch 202 causing the outer splines of bypass coupling 216 shift out of mesh with inner splines 228 of outer race 230, thereby shifting bypass assembly 204 to the disengaged position and selectable clutch assembly 200 to the unidirectional torque transfer mode, as best seen in figure 3A .
- actuation shaft 210 has returned to its first position relative to hydraulic cylinder 214 and is secured in the first position by ball-detent locking mechanism 220 as one or more balls are engaged with first detent groove 232 of actuation shaft 210.
- selectable clutch assembly 200 is shown with an optional feature of a blocking ring 236 used instead of wave spring 222 to overcome misalignment in the clocking of outer splines 238 of bypass coupling 216 and inner splines 228 of outer race 230.
- blocking ring 236 enhances the engagement sequence by providing alignment functionality between outer splines 238 of bypass coupling 216 and inner splines 228 of outer race 230.
- blocking ring 236 includes splines 240 the are positioned between outer splines 238 of bypass coupling 216 and inner splines 228 of outer race 230 as bypass coupling 216 moves toward outer race 230.
- blocking ring 236 is allowed to rotate slightly in one direction relative to outer race 230 but not in the other direction, which aids in aligning outer splines 238 of bypass coupling 216 with inner splines 228 of outer race 230.
- selectable clutch assembly 200 is shown with a ratchet assembly 242 for coupling bypass coupling 216 with outer race 230, according to an example not forming part of the claimed invention, but which may be useful for understanding features thereof.
- bypass coupling 216 including a plurality spring mounted keys 244 the are radially outwardly biased by one or more spring elements depicted as annular spring 246.
- mating profile 248 of outer race 230 compresses spring mounted keys 244 and rotates relative thereto as required to receive spring mounted keys 244 against shoulders 250 of mating profile 248.
- Locking spring assembly 300 is coupled to actuation shaft 210 and has a first relaxed position as depicted in figures 6A and 6D and a second relaxed position as depicted in figure 6C .
- the first relaxed position may represent the locked position of actuation shaft 210 when bypass assembly 204 is in the engaged position and selectable clutch assembly 200 is in the bidirectional torque transfer mode.
- the second relaxed position may represent the locked position of actuation shaft 210 when bypass assembly 204 is in the disengaged position and selectable clutch assembly 200 is in the unidirectional torque transfer mode.
- Locking spring assembly 300 maintains these locked positions as energy is require to compress the spring elements of diaphragm 302, as best seen in figure 6B , to shift actuation shaft 210 between its first and second positions.
Description
- The present disclosure relates, in general, to powertrains operable for use on rotorcraft and, in particular, to multimode powertrains operable to selectively utilize secondary engine power independent of or together with main engine power to drive the main rotor, the tail rotor and/or the accessories of a rotorcraft.
- Certain rotorcraft are capable of taking off, hovering and landing vertically. One such rotorcraft is a helicopter, which has one or more main rotors that provide lift and thrust to the aircraft. The main rotors not only enable hovering and vertical takeoff and landing, but also enable forward, backward and lateral flight. These attributes make helicopters highly versatile for use in congested, isolated or remote areas. Another such rotorcraft is a tiltrotor aircraft, which has a set of proprotors that can change their plane of rotation based on the operation being performed. Tiltrotor aircraft typically have a pair of nacelles mounted near the outboard ends of a fixed wing with each nacelle housing a propulsion system that provides torque and rotational energy to a proprotor. The nacelles are rotatable relative to the fixed wing such that the proprotors have a generally horizontal plane of rotation providing vertical thrust for takeoff, hovering and landing, much like a conventional helicopter, and a generally vertical plane of rotation providing forward thrust for cruising in forward flight with the fixed wing providing lift, much like a conventional propeller driven airplane.
- The power demand of a rotorcraft can change significantly based upon the operating mode of the rotorcraft. For example, significantly more power may be demanded during takeoff, hover or dash operations compared to cruise or preflight operations. Certain rotorcraft utilize auxiliary power units to supply preflight power during startup procedures and to start the main engine of the rotorcraft. It has been found, however, that these auxiliary power units are not operable to provide supplemental power or emergency power to the main rotor during flight operation.
-
US 3 362 255 describes a mechanism for transmitting power from a common power source to two, receiving members or groups of receiving members, comprising three coaxial shafts respectively connected permanently to said common power source and to said two members or groups of members, and coupled or decoupled in pairs by means of three automatically actuated clutching means interposed between each pair of shafts, a lock-out means avoiding any action of said first clutching means and means for preventing any accidental locking-in of the first clutching means -
US 2018/172088 describes a low-backlash multimode clutch including a one-way bearing allowing rotation in a first direction as well as a number of actuatable pawls in one race and a number of receiving slots having engagement faces in the other race. The engagement faces are tilted such that when the pawls are actuated, any torque applied in the first direction tends to force the pawls outward but the pawls are retained inward, such as by actuator rods. In this way, the one-way clutch may be selectively locked and unlocked with zero backlash against the one-way bearing. -
US 2019/032760 describes a switchable one-way clutch that is able to switch between operating as a one-way clutch and a clutch that locks in both directions. The clutch includes an inner race, and an outer race that includes an inner surface with a plurality of ramped profiles. A control plate is located radially outward from the inner race and moveable in an axial direction relative to the outer race. A plurality of rollers are contactable with the outer and inner races. A roller cage is configured to position and contain the plurality of rollers. A hydraulic piston is coupled to an actuator arm, such that movement of the piston along the axis moves the actuator arm along the axis. To switch and engage the clutch such that rotation is locked in both directions, the piston and actuator arm move axially to hold the control plate and attached roller cage against rotation. - In a first aspect, the present disclosure is directed to a selectable clutch assembly according to appended claim 1.
- In some embodiments, the freewheeling unit may be a sprag clutch.
- In some embodiments, the bypass assembly may include an actuator configured to shift the bypass assembly between the engaged position and the disengaged position. In certain embodiments, the bypass assembly may include a locking assembly configured to maintain the bypass assembly in the engaged position and in the disengaged position.
- In a second aspect, the present disclosure is directed to a multimode powertrain for a rotorcraft. The multimode powertrain includes a main drive system, a secondary drive system and a selectable clutch assembly according to appended claim 1 positioned between the main and the secondary drive systems.
- In some embodiments, the main drive system may include a main engine, a main rotor gearbox coupled to the main engine and a tail rotor gearbox coupled to the main rotor gearbox and the secondary drive system may include a secondary engine. In a preflight configuration, the selectable clutch assembly is in the disengaged position, the main engine is not operating and the secondary engine provides power to at least one rotorcraft accessory coupled to the secondary drive system. In an enhanced power configuration, the selectable clutch assembly is in the engaged position, the main engine provides power to the main rotor gearbox and the tail rotor gearbox and the secondary engine provides power to at least one rotorcraft accessory coupled to the secondary drive system and to the main drive system through the selectable clutch assembly. In a high efficiency configuration, the selectable clutch assembly is in the engaged position, the secondary engine is not operating, the main engine provides power to the main rotor gearbox, the tail rotor gearbox and the secondary drive system through the selectable clutch assembly to power at least one rotorcraft accessory coupled to the secondary drive system. In an enhanced auto rotation configuration, the selectable clutch assembly is in the engaged position, the main engine is not operating and the secondary engine provides power to the main drive system through the selectable clutch assembly including to the main rotor gearbox. In certain embodiments, the secondary engine may be configured to generate between about 5 percent and about 20 percent of the horsepower of the main engine. In other embodiments, the secondary engine may be configured to generate between about 10 percent and about 15 percent of the horsepower of the main engine.
- In a third aspect, the present disclosure is directed to a rotorcraft that includes a main drive system having a main engine, a main rotor gearbox coupled to the main engine and a tail rotor gearbox coupled to the main rotor gearbox. A main rotor is coupled to the main rotor gearbox and is rotatable thereby. A tail rotor is coupled to the tail rotor gearbox and is rotatable thereby. A secondary drive system includes a secondary engine. A selectable clutch assembly according to appended claim 1 is positioned between the main and the secondary drive systems.
- For a more complete understanding of the features and advantages of the present disclosure, reference is now made to the detailed description along with the accompanying figures in which corresponding numerals in the different figures refer to corresponding parts and in which:
-
Figures 1A-1C are schematic illustrations of a rotorcraft having a multimode powertrain in accordance with embodiments of the present disclosure; -
Figures 2A-2D are block diagrams of a multimode powertrain for a rotorcraft in various operating configurations in accordance with embodiments of the present disclosure; -
Figures 3A-3B are schematic illustrations of a selectable clutch assembly for use in a multimode powertrain of a rotorcraft in disengaged and engaged positions in accordance with embodiments of the present disclosure; -
Figures 4A-4B are schematic illustrations of a blocking ring operable to aid in the actuation of a selectable clutch assembly from the disengaged position to the engaged position in accordance with embodiments of the present disclosure; -
Figures 5A-5B are schematic illustrations of a selectable clutch assembly having a ratchet assembly in accordance with an example not forming part of the claimed invention, but which may be useful for understanding features thereof; and -
Figures 6A-6D are schematic illustrations of an alternate lock assembly for securing a selectable clutch assembly in the disengaged position and the engaged position in accordance with embodiments of the present disclosure. - While the making and using of various embodiments of the present disclosure are discussed in detail below, it should be appreciated that the present disclosure provides many applicable inventive concepts, which can be embodied in a wide variety of specific contexts. The specific embodiments discussed herein are merely illustrative and do not delimit the scope of the present disclosure. In the interest of clarity, all features of an actual implementation may not be described in this specification. It will of course be appreciated that in the development of any such actual embodiment, numerous implementation-specific decisions must be made to achieve the developer's specific goals, such as compliance with system-related and business-related constraints, which will vary from one implementation to another. Moreover, it will be appreciated that such a development effort might be complex and time-consuming but would nevertheless be a routine undertaking for those of ordinary skill in the art having the benefit of this disclosure.
- In the specification, reference may be made to the spatial relationships between various components and to the spatial orientation of various aspects of components as the devices are depicted in the attached drawings. However, as will be recognized by those skilled in the art after a complete reading of the present disclosure, the devices, members, apparatuses, and the like described herein may be positioned in any desired orientation. Thus, the use of terms such as "above," "below," "upper," "lower" or other like terms to describe a spatial relationship between various components or to describe the spatial orientation of aspects of such components should be understood to describe a relative relationship between the components or a spatial orientation of aspects of such components, respectively, as the devices described herein may be oriented in any desired direction. As used herein, the term "coupled" may include direct or indirect coupling by any means, including by mere contact or by moving and/or non-moving mechanical connections.
- Referring to
figures 1A-1C in the drawings, a rotorcraft in the form of a helicopter is schematically illustrated and generally designated 10. The primary propulsion assembly ofhelicopter 10 is amain rotor assembly 12.Main rotor assembly 12 includes a plurality ofrotor blades 14 extending radially outward from amain rotor hub 16.Main rotor assembly 12 is coupled to afuselage 18 and is rotatable relative thereto. The pitch ofrotor blades 14 can be collectively and/or cyclically manipulated to selectively control direction, thrust and lift ofhelicopter 10. Atailboom 20 is coupled tofuselage 18 and extends fromfuselage 18 in the aft direction. Ananti-torque system 22 includes atail rotor assembly 24 coupled to an aft end oftailboom 20.Anti-torque system 22 controls the yaw ofhelicopter 10 by counteracting the torque exerted onfuselage 18 bymain rotor assembly 12. In the illustrated embodiment,helicopter 10 includes avertical tail fin 26 that provide stabilization to helicopter 10 during high speed forward flight. In addition,helicopter 10 includeswing members 28 that extend laterally fromfuselage 18 andwing members 30 that extend laterally fromtailboom 20.Wing members helicopter 10, thereby reducing the lift requirement onmain rotor assembly 12 and increasing the top speed ofhelicopter 10Main rotor assembly 12 andtail rotor assembly 24 receive torque and rotational energy from amain engine 32.Main engine 32 is coupled to amain rotor gearbox 34 by suitable clutching and shafting.Main rotor gearbox 34 is coupled tomain rotor assembly 12 by amast 36 and is coupled totail rotor assembly 24 by tailrotor drive shaft 38. In the illustrated embodiment, asecondary engine 40 is coupled to tailrotor drive shaft 38 by asecondary engine gearbox 42 that provides suitable clutching therebetween. Together,main engine 40,main rotor gearbox 34, tailrotor drive shaft 38,secondary engine 40 andsecondary engine gearbox 42 as well as the various other shafts and gearboxes coupled therein may be considered as the multimode powertrain ofhelicopter 10. -
Secondary engine 40 is operable as an auxiliary power unit to provide preflight power to the accessories ofhelicopter 10 such as electric generators, hydraulic pumps and the like as well as to provide the power required to startmain engine 32. In addition,secondary engine 40 is operable to provide supplemental power that is additive with the power provided bymain engine 32 during, for example, high power demand conditions including takeoff, hover and dash operations.Secondary engine 40 is also operable to provide emergency power tomain rotor assembly 12. For example, in the event of a failure ofmain engine 32,secondary engine 40 is operable to provide emergency power to enhance the autorotation and flare recovery maneuver ofhelicopter 10. Use ofsecondary engine 40 not only enhances the safety ofhelicopter 10 but also increases the efficiency ofhelicopter 10. For example, having the extra power provided bysecondary engine 40 during high power demand operations allowsmain engine 32 to be downsized for more efficient single engine operations such as during cruise operations. - It should be appreciated that
helicopter 10 is merely illustrative of a variety of aircraft that can implement the embodiments disclosed herein. Indeed, the multimode powertrain of the present disclosure may be implemented on any rotorcraft. Other aircraft implementations can include hybrid aircraft, tiltwing aircraft, tiltrotor aircraft, quad tiltrotor aircraft, unmanned aircraft, gyrocopters, propeller-driven airplanes, compound helicopters, drones and the like. As such, those skilled in the art will recognize that the multimode powertrain of the present disclosure can be integrated into a variety of aircraft configurations. It should be appreciated that even though aircraft are particularly well-suited to implement the embodiments of the present disclosure, non-aircraft vehicles and devices can also implement the embodiments. Referring tofigures 2A-2D in the drawings, various operating configurations of amultimode powertrain 100 for a rotorcraft are illustrated in a block diagram format.Multimode powertrain 100 includes amain engine 102 such as a turbo shaft engine capable of producing 2000 to 4000 horsepower or more, depending upon the particular implementation.Main engine 102 is coupled to a freewheeling unit depicted as sprag clutch 104 that acts as a one-way clutch enabling a driving mode wherein torque frommain engine 102 is coupled tomain rotor gearbox 106 when the input side rotating speed tosprag clutch 104 is matched with the output side rotating speed fromsprag clutch 104. For convenience of illustration, the input side of sprag clutch 104 is depicted as the apex of the greater than symbol and the output side of sprag clutch 104 is depicted as the open end of the greater than symbol. Importantly,sprag clutch 104 has an over running mode whereinmain engine 102 is decoupled frommain rotor gearbox 106 when the input side rotating speed ofsprag clutch 104 is less than the output side rotating speed ofsprag clutch 104.Operating sprag clutch 104 in the over running mode allows, for example,main rotor 108 ofhelicopter 10 to engage in autorotation in the event of a failure ofmain engine 102. - In the illustrated embodiment,
main rotor gearbox 106 is coupled to sprag clutch 104 via a suitable drive shaft. In addition,main rotor gearbox 106 is coupled tomain rotor 108 by a suitable mast.Main rotor gearbox 106 includes a gearbox housing and a plurality of gears, such as planetary gears, used to adjust the engine output to a suitable rotational speed so thatmain engine 102 andmain rotor 108 may each rotate at optimum speed during flight operations ofhelicopter 10.Main rotor gearbox 106 is coupled to atail rotor gearbox 110 via a suitable tail rotor drive shaft.Tail rotor gearbox 110 includes a gearbox housing and a plurality of gears that may adjust the main rotor gearbox output to a suitable rotational speed for operation oftail rotor 112.Main engine 102,sprag clutch 104,main rotor gearbox 106 andtail rotor gearbox 110 as well as the various shafts and gearing systems coupled therewith may be considered the main drive system ofmultimode powertrain 100. -
Multimode powertrain 100 includes asecondary engine 114 such as a turbo shaft engine capable of producing 200 to 400 horsepower or more, depending upon the particular implementation. In the illustrated embodiment,secondary engine 114 may generate between about 5 percent and about 20 percent of the horsepower ofmain engine 102. In other embodiments,secondary engine 114 may generate between about 10 percent and about 15 percent of the horsepower ofmain engine 102.Secondary engine 114 is coupled to a freewheeling unit depicted as sprag clutch 116 that acts as a one-way clutch enabling a driving mode wherein torque fromsecondary engine 114 is coupled through sprag clutch 116 from the input side to the output side. Importantly,sprag clutch 116 has an over running mode whereinsecondary engine 114 is decoupled from torque transfer with sprag clutch 116 when the input side rotating speed ofsprag clutch 116 is less than the output side rotating speed ofsprag clutch 116.Operating sprag clutch 116 in the over running mode allows, for example,main engine 102 to drive the rotorcraft accessories such as one ormore generators 118, one or morehydraulic pumps 120 orother accessories 122 whensecondary engine 114 is not operating, as discussed herein.Secondary engine 114 and sprag clutch 116 as well as the various shafts and gearing systems coupled therewith may be considered the secondary drive system ofmultimode powertrain 100. - Disposed between the main drive system and the secondary drive system of
multimode powertrain 100 is a selectableclutch assembly 124 that has a unidirectional torque transfer mode and a bidirectional torque transfer mode. In the unidirectional torque transfer mode of selectableclutch assembly 124, torque can be driven from the main drive system to the secondary drive system ofmultimode powertrain 100 but torque cannot be driven from the secondary drive system to the main drive system ofmultimode powertrain 100. In the bidirectional torque transfer mode of selectableclutch assembly 124, torque can be driven from the main drive system to the secondary drive system ofmultimode powertrain 100 and torque can be driven from the secondary drive system to the main drive system ofmultimode powertrain 100. In the illustrated embodiment, selectableclutch assembly 124 includes a freewheeling unit depicted assprag clutch 126 and abypass assembly 128. Sprag clutch 126 acts as a one-way clutch enabling a driving mode wherein torque from the main drive system is coupled through sprag clutch 126 from the input side to the output side. Sprag clutch 126 also has an over running mode wherein the main drive system is decoupled from torque transfer with sprag clutch 126 when the input side rotating speed ofsprag clutch 126 is less than the output side rotating speed ofsprag clutch 126. When the over running mode of sprag clutch 126 is enabled, selectableclutch assembly 124 is in its unidirectional torque transfer mode. The over running mode of selectableclutch assembly 124 can be disabled by engagingbypass assembly 128 withsprag clutch 126. Whenbypass assembly 128 prevents sprag clutch 126 from operating in the over running mode, selectableclutch assembly 124 is in its bidirectional torque transfer mode. - In
figure 2A ,multimode powertrain 100 is in a preflight configuration in whichmain engine 102 is not yet operating as indicated by the dashed lines between the components of the main drive system. As the main drive system is not turning, no torque is being applied to selectableclutch assembly 124 as indicated by the dashed lines therebetween. In addition, selectableclutch assembly 124 is in the unidirectional torque transfer mode whereinbypass assembly 128 is disengaged fromsprag clutch 126. In the preflight configuration,secondary engine 114 is operating and providing torque and rotational energy within the secondary drive system, as indicated by the solid lines and arrowheads. More specifically,secondary engine 114 is driving the input side of sprag clutch 116, which causes the output side of sprag clutch 116 to drive an output shaft and/or output gear system. The output torque from sprag clutch 116 is used to drive the rotorcraft accessories such as one ormore generators 118, one or morehydraulic pumps 120 as well asother accessories 122. While operating in the preflight configuration, the pilot ofhelicopter 10 can proceed through the startup procedure and can use power fromsecondary engine 114 to startmain engine 102. - Once
main engine 102 is operating, torque is delivered through the main drive system as indicated by the solid lines and arrowheads between the components within the main drive system, as best seen infigure 2B . In addition, as the main drive system is turning, torque may be applied to selectableclutch assembly 124. As discussed herein, in order to shift selectableclutch assembly 124 from the unidirectional torque transfer mode to the bidirectional torque transfer mode, power should be applied to the input side of sprag clutch 126 from the main drive system such that the input side and the output side of sprag clutch 126 are turning together.Bypass assembly 128 can now be actuated from the disengaged position to the engaged position placing selectableclutch assembly 124 in the bidirectional torque transfer mode. The operations of engaging and disengagingbypass assembly 128 may be pilot controlled and/or may be automated by the flight control computer ofhelicopter 10 and may determined according to the operating conditions ofhelicopter 10. In this configuration, power fromsecondary engine 114 may not only drive the rotorcraft accessories but may also be used to augment the power ofmain engine 102 within the main drive system, as indicated by the solid lines and arrowhead from selectableclutch assembly 124 to the main drive system infigure 2B . This configuration may be referred to as the enhanced power configuration ofmultimode powertrain 100 whereinmain engine 102 andsecondary engine 114 are operating together and selectableclutch assembly 124 is in the bidirectional torque transfer mode. The enhanced power configuration ofmultimode powertrain 100 is particularly useful during high power demand operations such as during takeoff, hover or dash operations. - Once
helicopter 10 has completed a takeoff, it may be desirable to shut downsecondary engine 114 and operatehelicopter 10 in the high efficiency configuration ofmultimode powertrain 100, as best seen infigure 2C . In this configuration,secondary engine 114 is shut down as indicated by the dashed line betweensecondary engine 114 andsprag clutch 116. Also, in this configuration, torque and rotational energy are transferred frommain engine 102 through the main drive system to selectableclutch assembly 124, as indicated by the solid lines and arrowhead therebetween. The input power is transferred through selectableclutch assembly 124 and is output to drive the rotorcraft accessories such as one ormore generators 118, one or morehydraulic pumps 120 as well asother accessories 122. It is noted that rotational energy is also sent to sprag clutch 116, which is operating in its over running mode whilesecondary engine 114 is not operating. Thus, in addition to poweringmain rotor 108 andtail rotor 112, in the high efficiency configuration ofmultimode powertrain 100,main engine 102 also powers all of the accessories ofhelicopter 10. It should be noted that selectableclutch assembly 124 is preferably maintained in its bidirectional torque transfer mode during all flight operations. Selectableclutch assembly 124, however, is a fail safe component in that even if selectableclutch assembly 124 is shifted to the disengaged position and thus the unidirectional torque transfer mode,main engine 102 still drives torque and rotation energy through selectableclutch assembly 124 to operate the rotorcraft accessories. - In addition, it is preferred that selectable
clutch assembly 124 be maintained in its bidirectional torque transfer mode as a safety feature in the event of a failure inmain engine 102 during flight, as indicated by the dashed lines betweenmain engine 102 and sprag clutch 104 infigure 2D . In this case, an autorotation maneuver may be performed in which the descent rate ofhelicopter 10 is reduced using the aerodynamic force of the air moving up throughmain rotor 108. Upon final approach during the autorotation landing,helicopter 10 then performs a flare recovery maneuver in which the kinetic energy ofmain rotor 108 is converted into lift using aft cyclic control. Both the autorotation maneuver and the flare recovery maneuver are enhanced by operatingsecondary engine 114 and sending power through selectableclutch assembly 124 to the main drive system, as indicated by the solid lines and arrowhead therebetween, and more particularly by sending power tomain rotor 108 as indicated by the solid lines and arrowheads leading thereto. It is noted that rotational energy is also sent to sprag clutch 104, which is operating in its over running mode whilemain engine 102 is not operating. This configuration may be referred to as the enhanced autorotation configuration ofmultimode powertrain 100 whereinmain engine 102 is down butsecondary engine 114 is providing power tomain rotor 108 through selectableclutch assembly 124, which is in the bidirectional torque transfer mode. - Referring to
figures 3A-3B in the drawings, a selectable clutch assembly is schematically illustrated and generally designated 200. Selectableclutch assembly 200 includes a freewheeling unit depicted assprag clutch 202 and abypass assembly 204. As discussed herein, selectableclutch assembly 200 has a unidirectional torque transfer mode and a bidirectional torque transfer mode. In the unidirectional torque transfer mode, torque can be driven from the input ofside sprag clutch 202, includinginput gear 205, to the output side of sprag clutch 202, includingoutput gear 206, but torque cannot be driven fromoutput gear 206 to inputgear 205. In the bidirectional torque transfer mode, torque can be driven frominput gear 205 tooutput gear 206 and torque can be driven fromoutput gear 206 to inputgear 205. For example, in the unidirectional torque transfer mode, selectableclutch assembly 200 operates with the functionality of sprag clutch 202 wherein torque and rotational energy from the main drive system ofhelicopter 10, which is coupled toinput gear 205, is operable to drive the secondary drive system ofhelicopter 10, which is coupled tooutput gear 206. Torque and rotational energy from the secondary drive system ofhelicopter 10, however, is not operable to drive the main drive system ofhelicopter 10 assprag clutch 202 will be operating in its over running mode. As another example, in the bidirectional torque transfer mode, selectableclutch assembly 200 operates with the functionality of a connected shaft wherein torque and rotational energy from the main drive system ofhelicopter 10 is operable to drive the secondary drive system ofhelicopter 10 and torque and rotational energy from the secondary drive system ofhelicopter 10 is operable to drive the main drive system ofhelicopter 10. - Selectable
clutch assembly 200 is operated between the unidirectional and bidirectional torque transfer modes by actuatingbypass assembly 204 between its disengaged and engaged positions. In the illustrated embodiment,bypass assembly 204 includes an actuator depicted ashydraulic actuator 208. In other embodiments, the actuator ofbypass assembly 204 could be an electrical actuator, a mechanical actuator or other suitable actuation device.Hydraulic actuator 208 includes anactuation shaft 210 that is movable between first and second positions responsive to hydraulic pressure operating on apiston end 212 ofactuation shaft 210, which is disposed within ahydraulic cylinder 214 ofhydraulic actuator 208.Actuation shaft 210 is coupled to bypasscoupling 216 at bearingassembly 218 that provides for relative rotation therebetween. In the illustrated embodiment,bypass assembly 204 includes a mechanical locking assembly depicted as ball-detent locking mechanism 220. A biasing element depicted aswave spring 222 is positioned betweenactuation shaft 210 and bearingassembly 218. - In
figure 3A , selectableclutch assembly 200 is in the unidirectional torque transfer mode whereinbypass assembly 204 is in the disengaged position. As illustrated,inner splines 224 ofbypass coupling 216 are in mesh with outer splines (not visible) ofinner shaft 226 of the output side ofsprag clutch 202. As such, when the output side of sprag clutch 202 is rotating,bypass coupling 216 also rotates. Outer splines (not visible) ofbypass coupling 216 are out of mesh withinner splines 228 ofouter race 230 of the input side ofsprag clutch 202. As such,bypass coupling 216 may rotate independent of the input side of sprag clutch 202 when sprag clutch 202 is operating in its over running mode. In this disengaged position,actuation shaft 210 is in its first position relative tohydraulic cylinder 214 and is secured in the first position by ball-detent locking mechanism 220 as one or more balls are engaged with afirst detent groove 232 ofactuation shaft 210. - When it is desired to operate selectable
clutch assembly 200 from the unidirectional to the bidirectional torque transfer mode, the input side of sprag clutch 202 is used to drive the output side of sprag clutch 202 such thatbypass coupling 216 andouter race 230 will be rotating at the same speed. Hydraulic pressure may then be used to biasactuation shaft 210 towardsprag clutch 202. When the force onpiston end 212 is sufficient to overcome the locking force generated by ball-detent locking mechanism 220,actuation shaft 210 will shift toward sprag clutch 202 causing the outer splines ofbypass coupling 216 to mesh withinner splines 228 ofouter race 230, thereby shiftingbypass assembly 204 to the engaged position and selectableclutch assembly 200 to the bidirectional torque transfer mode, as best seen infigure 3B .Wave spring 222 assists in overcoming any misalignment in the clocking of the outer splines ofbypass coupling 216 andinner splines 228 ofouter race 230 by allowing full actuation ofactuation shaft 210 while maintaining pressure betweenbypass coupling 216 andouter race 230 so that wheninner shaft 226 andouter race 230 start to rotate relative to each other, outer splines ofbypass coupling 216 will mesh withinner splines 228 ofouter race 230. Oncebypass assembly 204 is in the engaged position,actuation shaft 210 is in its second position relative tohydraulic cylinder 214 and is secured in the second position by ball-detent locking mechanism 220 as one or more balls are engaged with asecond detent groove 234 ofactuation shaft 210. In this bidirectional torque transfer mode of selectableclutch assembly 200, when the output side of sprag clutch 202 is rotating,bypass coupling 216 rotates therewith. Likewise, when the input side of sprag clutch 202 is rotating,bypass coupling 216 rotates therewith, thereby bypassing the over running mode of sprag clutch 202 such that selectableclutch assembly 200 operates with the functionality of a connected shaft. - When it is desired to operate selectable
clutch assembly 200 from the bidirectional to the unidirectional torque transfer mode, the input side of sprag clutch 202 preferably drives the output side ofsprag clutch 202. Hydraulic pressure may then be used to biasactuation shaft 210 away fromsprag clutch 202. When the force onpiston end 212 is sufficient to overcome the locking force generated by ball-detent locking mechanism 220,actuation shaft 210 will shift away from sprag clutch 202 causing the outer splines ofbypass coupling 216 shift out of mesh withinner splines 228 ofouter race 230, thereby shiftingbypass assembly 204 to the disengaged position and selectableclutch assembly 200 to the unidirectional torque transfer mode, as best seen infigure 3A . Oncebypass assembly 204 is in the disengaged position,actuation shaft 210 has returned to its first position relative tohydraulic cylinder 214 and is secured in the first position by ball-detent locking mechanism 220 as one or more balls are engaged withfirst detent groove 232 ofactuation shaft 210. - Referring to
figures 4A-4B in the drawings, selectableclutch assembly 200 is shown with an optional feature of ablocking ring 236 used instead ofwave spring 222 to overcome misalignment in the clocking ofouter splines 238 ofbypass coupling 216 andinner splines 228 ofouter race 230. In the illustrated embodiment, blockingring 236 enhances the engagement sequence by providing alignment functionality betweenouter splines 238 ofbypass coupling 216 andinner splines 228 ofouter race 230. As best seen in the progression depicted infigure 4B , blockingring 236 includessplines 240 the are positioned betweenouter splines 238 ofbypass coupling 216 andinner splines 228 ofouter race 230 asbypass coupling 216 moves towardouter race 230. Preferably, blockingring 236 is allowed to rotate slightly in one direction relative toouter race 230 but not in the other direction, which aids in aligningouter splines 238 ofbypass coupling 216 withinner splines 228 ofouter race 230. - Referring to
figures 5A-5B in the drawings, selectableclutch assembly 200 is shown with aratchet assembly 242 forcoupling bypass coupling 216 withouter race 230, according to an example not forming part of the claimed invention, but which may be useful for understanding features thereof. - Instead of using
wave spring 222 to aid in the alignmentouter splines 238 ofbypass coupling 216 andinner splines 228 ofouter race 230 during the engagement sequence, in the illustrated embodiment,bypass coupling 216 including a plurality spring mountedkeys 244 the are radially outwardly biased by one or more spring elements depicted asannular spring 246. Asbypass coupling 216 approaches and contactsouter race 230 during the engagement sequence,mating profile 248 ofouter race 230 compresses spring mountedkeys 244 and rotates relative thereto as required to receive spring mountedkeys 244 againstshoulders 250 ofmating profile 248. - Referring to
figures 6A-6D in the drawings, an alternate embodiment of a mechanical locking assembly for a selectable clutch assembly is schematically illustrated and generally designated 300. Lockingspring assembly 300 is coupled toactuation shaft 210 and has a first relaxed position as depicted infigures 6A and 6D and a second relaxed position as depicted infigure 6C . The first relaxed position may represent the locked position ofactuation shaft 210 whenbypass assembly 204 is in the engaged position and selectableclutch assembly 200 is in the bidirectional torque transfer mode. Likewise, the second relaxed position may represent the locked position ofactuation shaft 210 whenbypass assembly 204 is in the disengaged position and selectableclutch assembly 200 is in the unidirectional torque transfer mode. Lockingspring assembly 300 maintains these locked positions as energy is require to compress the spring elements ofdiaphragm 302, as best seen infigure 6B , to shiftactuation shaft 210 between its first and second positions. - The foregoing description of embodiments of the disclosure has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure to the precise form disclosed, and modifications and variations are possible in light of the above teachings or may be acquired from practice of the disclosure. The embodiments were chosen and described in order to explain the principals of the disclosure and its practical application to enable one skilled in the art to utilize the disclosure in various embodiments and with various modifications as are suited to the particular use contemplated.
Claims (12)
- A selectable clutch assembly (124) comprising:a freewheeling unit (116) having an input side with inner splines (228) and an output side with outer splines, the freewheeling unit (116) having a driving mode wherein torque applied to the input side is transferred to the output side and an over running mode wherein torque applied to the output side is not transferred to the input side; anda bypass assembly (128) having a bypass coupling (216) with inner splines (224) and outer splines, the inner splines (224) of the bypass coupling (216) coupled to the outer splines of the output side of the freewheeling unit (116) such that the bypass assembly (128) is rotatable with the output side of the freewheeling unit (116), the bypass assembly (128) actuatable between an engaged position in which the outer splines of the bypass coupling (216) are coupled to the inner splines (228) of the input side of the freewheeling unit (116) and a disengaged position in which the outer splines of the bypass coupling (216) are not coupled to the inner splines (228) of the input side of the freewheeling unit (116);wherein, in the disengaged position of the bypass assembly, the freewheeling unit (116) is operable in the driving mode and the over running mode such that the selectable clutch assembly (124) is configured for unidirectional torque transfer from the input side to the output side; andwherein, in the engaged position of the bypass assembly, the over running mode of the freewheeling unit (116) is disabled such that the selectable clutch assembly (124) is configured for bidirectional torque transfer from the input side to the output side and from the output side to the input side.
- The selectable clutch assembly (124) as recited in claim 1 wherein the freewheeling unit (116) comprises a sprag clutch.
- The selectable clutch assembly (124) as recited in claim 1 or in any preceding claim wherein the bypass assembly (128) further comprises an actuator (208) configured to shift the bypass assembly (128) between the engaged position and the disengaged position.
- The selectable clutch assembly (124) as recited in claim 1 or in any preceding claim wherein the bypass assembly (128) further comprises a locking assembly configured to maintain the bypass assembly (128) in the engaged position and in the disengaged position.
- A multimode powertrain (100) for a rotorcraft, the multimode powertrain (100) comprising:a main drive system;a secondary drive system; andthe selectable clutch assembly (124) of claim 1 positioned between the main and the secondary drive systems, wherein:
the input side of the freewheeling unit (116) is coupled to the main drive system and the output side is coupled to the secondary drive system. - The multimode powertrain (100) as recited in claim 5
wherein the main drive system further comprises a main engine (102), a main rotor gearbox (106) coupled to the main engine (102) and a tail rotor (112) gearbox coupled to the main rotor gearbox (106) and wherein the secondary drive system further comprises a secondary engine (114). - A rotorcraft comprising:a main drive system including a main engine (102), a main rotor gearbox (106) coupled to the main engine (102) and a tail rotor (112) gearbox coupled to the main rotor gearbox (106);a main rotor coupled to the main rotor gearbox (106) and rotatable thereby;a tail rotor (112) coupled to the tail rotor (112) gearbox and rotatable thereby;a secondary drive system including a secondary engine (114); andthe selectable clutch assembly (124) of claim 1 positioned between the main and the secondary drive systems, and wherein:
the input side of the freewheeling unit (116) is coupled to the main drive system and the output side is coupled to the secondary drive system. - The multimode powertrain (100) as recited in claim 6 or the rotorcraft as recited in claim 7 wherein, in a preflight configuration, the selectable clutch assembly (124) is in the disengaged position, the main engine (102) is not operating and the secondary engine (114) provides power to at least one rotorcraft accessory coupled to the secondary drive system.
- The multimode powertrain (100) as recited in claim 6 or in claim8, or the rotorcraft as recited claim 7 or in claim 8 wherein, in an enhanced power configuration, the selectable clutch assembly (124) is in the engaged position, the main engine (102) provides power to the main rotor gearbox (106) and the tail rotor (112) gearbox and the secondary engine (114) provides power to at least one rotorcraft accessory coupled to the secondary drive system and to the main drive system through the selectable clutch assembly.
- The multimode powertrain (100) as recited in claim 6 or in claim 8 or in claim 9, or the rotorcraft as recited in claim 7 or claim 8 or claim 9 wherein, in a high efficiency configuration, the selectable clutch assembly (124) is in the engaged position, the secondary engine (114) is not operating, and the main engine (102) provides power to the main rotor gearbox (106), the tail rotor (112) gearbox and the secondary drive system through the selectable clutch assembly (124) to power at least one rotorcraft accessory coupled to the secondary drive system.
- The multimode powertrain (100) as recited in claim 6 or in any of claims 8 to 10, or the rotorcraft as recited in claim 7 or in any of claims 8 to 10 wherein, in an enhanced autorotation configuration, the selectable clutch assembly (124) is in the engaged position, the main engine (102) is not operating and the secondary engine (114) provides power to the main drive system through the selectable clutch assembly (124) including to the main rotor gearbox (106).
- The multimode powertrain (100) as recited in claim 6 or in any of claims 8 to 11, or the rotorcraft as recited in claim 7 or any preceding rotorcraft claim wherein the secondary engine (114) is configured to generate between about 5 percent and about 20 percent of the power of the main engine (102), or wherein the secondary engine (114) is configured to generate between about 10 percent and about 15 percent of the power of the main engine (102).
Applications Claiming Priority (2)
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US201962801621P | 2019-02-05 | 2019-02-05 | |
US16/274,520 US10788088B2 (en) | 2019-02-05 | 2019-02-13 | Multimode powertrains for rotorcraft |
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EP3693627A1 EP3693627A1 (en) | 2020-08-12 |
EP3693627B1 true EP3693627B1 (en) | 2022-03-09 |
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EP20152333.9A Active EP3693627B1 (en) | 2019-02-05 | 2020-01-17 | Multimode powertrains for rotorcraft |
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US11174014B2 (en) | 2019-02-05 | 2021-11-16 | Textron Innovations Inc. | Failsafe multimode clutch assemblies for rotorcraft |
US11174015B2 (en) | 2019-02-05 | 2021-11-16 | Textron Innovations Inc. | Multimode clutch assemblies having engagement status sensors |
US11174013B2 (en) | 2019-02-05 | 2021-11-16 | Textron Innovations Inc. | Failsafe multimode clutch assemblies for rotorcraft |
US11708868B2 (en) | 2019-02-13 | 2023-07-25 | Textron Innovations Inc. | Failsafe multimode clutch assemblies for rotorcraft |
US11873081B2 (en) | 2021-06-09 | 2024-01-16 | Textron Innovations Inc. | Supplemental engine power control |
IT202200000245A1 (en) | 2022-01-10 | 2023-07-10 | Torino Politecnico | Device for converting reciprocating motion into continuous rotary motion |
US20240017823A1 (en) * | 2022-07-18 | 2024-01-18 | Textron Innovations Inc. | Optimizing usage of supplemental engine power |
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FR1422328A (en) * | 1964-11-13 | 1965-12-24 | Sud Aviation | Improvements in power transmission mechanisms and their applications, particularly in helicopters |
US3455182A (en) | 1967-04-12 | 1969-07-15 | Garrett Corp | Helicopter lift augmentation means |
US5271295A (en) * | 1990-12-12 | 1993-12-21 | Aerospatiale Societe Nationale Industrielle | Mechanism for transmitting power between a driving shaft and two assemblies to be driven |
US6098921A (en) | 1999-05-06 | 2000-08-08 | Piasecki Aircraft Corp. | Rotary wing aircraft supplementary power drive system |
US7296767B2 (en) * | 2005-05-31 | 2007-11-20 | Sikorsky Aircraft Corporation | Variable speed transmission for a rotary wing aircraft |
US20090078525A1 (en) * | 2007-09-26 | 2009-03-26 | The Timken Company | Method and Apparatus For Limiting Wheel End Clutch Ring Travel |
US8960031B2 (en) * | 2009-09-01 | 2015-02-24 | Parker-Hannifin Corporation | Aircraft stabilizer actuator |
US8950700B2 (en) | 2010-11-02 | 2015-02-10 | Groen Brothers Aviation, Inc. | Rotor driven auxiliary power apparatus and method |
FR3021629B1 (en) | 2014-05-28 | 2016-06-10 | Airbus Helicopters | BRAKE MACHINE EQUIPPED WITH A FUEL SUPPLY INSTALLATION OF A POWER UNIT COMPRISING AN AUXILIARY POWER UNIT (APU) |
US10040566B2 (en) | 2014-09-23 | 2018-08-07 | Sikorsky Aircraft Corporation | Hybrid contingency power drive system |
US10577118B2 (en) * | 2016-04-27 | 2020-03-03 | Pratt & Whitney Canada Corp. | Power plant management system for dual engine helicopter in single engine operation mode |
US20180086444A1 (en) * | 2016-09-23 | 2018-03-29 | Bell Helicopter Textron Inc. | Aircraft Drive System |
CN108223613B (en) | 2016-12-15 | 2021-02-02 | 博格华纳公司 | Low backlash multimode clutch |
US10451159B2 (en) | 2017-07-28 | 2019-10-22 | Schaeffler Technologies AG & Co. KG | Switchable one-way clutch |
-
2019
- 2019-02-13 US US16/274,520 patent/US10788088B2/en active Active
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EP3693627A1 (en) | 2020-08-12 |
US20200248760A1 (en) | 2020-08-06 |
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